Surface controlled subsurface safety valve

ABSTRACT

A safety valve for subsurface disposal equipped with an interfacing element of elastomeric and non-elastomeric components. The components include an elastomeric energizing component and a non-elastomeric seal ring configured to work together in attaining an internal seal sufficient for allowing the valve to remain consistently closed. Indeed, the aid afforded by the interfacing element may allow the valve to remain consistently and effectively closed even in particularly low pressure well environments or those of widely varying temperatures.

PRIORITY CLAIM/CROSS REFERENCE TO RELATED APPLICATION(S)

This Patent Document claims priority under 35 U.S.C. §119 to U.S. Provisional App. Ser. No. 61/526,067, filed on Aug. 22, 2011, and entitled, “Low Gas Migration System for Surface Controlled Subsurface Safety Valve”, incorporated herein by reference in its entirety.

BACKGROUND

Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. In recognition of these expenses, added emphasis has been placed on efficiencies associated with well completions and maintenance over the life of the well. Over the years, ever increasing well depths and sophisticated architecture have made reductions in time and effort spent in completions and maintenance operations of even greater focus. Similarly, increased safeguards in terms of hardware design may help minimize expenditures when operational interruptions do occur.

In terms of overall architecture and hardware, the well may be outfitted with a ‘tree’ of pressure regulating equipment and conventional well head at the oilfield surface. Additionally, safety valves, packers and other hardware may be incorporated into well tubular architecture as a manner by which to help regulate or manage subsurface fluid activity. For example, a surface controlled subsurface safety valve may be incorporated into the well tubular immediately below the well head. Thus, as described further below, safeguard may be provided for closing off well production, such as in the event of a loss of well control.

A surface controlled subsurface safety valve is a valve through which all fluids pass which are obtained from the well. That is, the production tubular extending below the well head and providing all of the access to the well may include this safety valve so as to allow production to be shut off when this valve is closed. For example, this may occur when the operator at the oilfield surface is alerted to a hazardous condition which may require the halting of production. However, the safety valve may be even more beneficial in circumstances where an automatic shut-off is required in the face of an unexpected loss of well control or other sudden, potentially hazardous event.

In order to achieve immediate, or near immediate, shut-off for circumstances as noted above, the valve is configured in a manner to be ‘normally closed’, for example, in the absence of positive hydraulic pressure directed thereat. Thus, should a sudden event emerge at the well head or nearby, the resulting loss of hydraulic pressure or other actuating force at the valve would result in its closure. As a result, production may be sealed off and terminated at a point below the well head until such time as it may safely be restored. That is, once issues at the well head or other potentially impaired surface control equipment have been adequately addressed.

Effective use of a surface controlled subsurface safety valve as indicated depends on both surface conditions and subsurface conditions. For example, as noted above, the surface conditions of well or operator control may lead to valve closure. However, effectively achieving a full seal with the valve is also aided in part based on subsurface conditions. So, for example, where the valve is of a flapper configuration, its completed closure is aided by the pressure of the well at a point below the valve. Indeed, pressure of over about 50-75 PSI from a point below the flapper is generally sufficient to ensure an effective seal of the valve and a complete halt to fluid production.

Unfortunately, in many circumstances, the pressure in the well is well below the above noted range and may be largely negligible altogether. When this is the case, the flapper may fail to achieve full closure due the lack of additional pressure support from the well. As a result, a slow, but nevertheless hazardous, migrating leakage of gaseous production fluid is often the case. That is, even where an attempted shut-off takes place due to a surface related emergency, hazardous production may continue to spill out from the well.

The reason for the lack of complete valve closure without the added aid of well pressure relates to the manner in which the closure takes place. That is, presently, a hydraulic piston is utilized such that positive hydraulic pressure is translated into a spring compression that that opens the valve. Thus, in theory, when the hydraulic pressure is removed as directed by surface conditions, the spring is allowed to expand and result in valve closure.

Unfortunately, without the aid of higher pressure from below the valve, the flapper is not assured to maintain an uninterrupted seal. Thus, as a practical matter, the corresponding failure of the adjacent hydraulic piston will allow for the migration of fluids uphole past the entire valve assembly. In sum, conventional surface controlled subsurface safety valves are often ineffective safeguards when utilized in conjunction with particularly low pressure wells.

SUMMARY

A surface controlled subsurface safety valve is disclosed having a valve housing coupled to a hydraulic line for running to an oilfield surface. The housing is coupled to the line at a valve seat thereof. A valve element disposed in the housing is configured for closing at an interface of the seat. The element includes an elastomeric energizing component adjacent a non-elastomeric seal ring for meeting the interface upon the valve closure. Of course, this summary is provided to introduce a selection of concepts that are further described below and is not intended as an aid in limiting the scope of the claimed subject matter.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side sectional view of an embodiment of a surface controlled subsurface safety valve.

FIG. 2 is an enlarged view of an embodiment of an internal sealing interface of the valve taken from 2-2 of FIG. 1.

FIG. 3 is an enlarged view of an embodiment of an energized valve element with a non-elastomeric seal ring taken from 3-3 at the interface of FIG. 2.

FIG. 4A is a side sectional view of an embodiment of a downhole tubular assembly incorporating the valve of FIG. 1 in an open position.

FIG. 4B is a side sectional view of the assembly of FIG. 4A with the valve of FIG. 1 in a closed position.

FIG. 5 is an overview of an oilfield having a well accommodating the assembly of FIGS. 4A and 4B therein.

FIG. 6 is a flow-chart summarizing an embodiment of employing a surface controlled subsurface safety valve.

DETAILED DESCRIPTION

Embodiments are described with reference to certain valve positioning in particular oilfield environments. For example, embodiments depicted herein reveal a valve assembly for incorporation immediately below a well head of conventional land based equipment. However, embodiments of safety valves as detailed herein may be suitable for offshore operations or further subsurface positioning. Regardless, the valve is outfitted with an element that includes an energized portion in conjunction with a non-elastomeric ring. Thus, not only is the valve configured for achieving effective sealable closure in low pressure well environments, it is also well suited for repeated use without undue concern over damage and premature failure.

Referring now to FIG. 1, a side sectional view of an embodiment of a surface controlled subsurface safety valve assembly 101 is shown. The assembly 101 is disposed within a housing 180 that may be incorporated into an oilfield tubular 581 (see FIG. 5). Thus, with added reference to FIGS. 4A and 4B, the assembly 101 may be utilized to govern the production of fluids 400 from downhole locations therebelow. More specifically, the assembly 101 may be equipped with a valve 190 including a flapper 490, or other suitable regulating mechanism, which may be open or closed. As such, a flow of fluid 400 through a central channel 110 of the assembly 101 may be allowed or prevented depending on whether or not the valve 190 is open or closed.

Setting the valve 190 to an open or closed position is determined by an internal spring 185, or other suitably responsive element, located adjacent the valve 190. In the embodiment of FIG. 1, the spring 185 is in a compressed state similar to that of FIG. 4A. Thus, the valve 190 is in an open position so as to allow a flow of fluid 400 to pass from a location below the valve 190 to a location uphole thereof (see FIG. 4A). Of particular note, the safety valve assembly 101 is configured such that maintaining the valve 190 in an open position requires compression of the spring 185 and thus, affirmative force being applied thereto. In this manner, the valve 190 may be less likely opened as a matter of accident or malfunction, but rather, more likely the result of a conscious operator instruction as further described below.

Continuing with reference to FIG. 1, affirmative opening of the valve 190 is achieved by the application of pressure which is applied to a hydraulic piston 125. The piston 125 may be a ⅛ to ⅝ inch rod stabilized by a surrounding housing 150. More notably, the piston 125 may be anchored to a head 175 which in turn acts on the spring 185 in order to attain the depicted compression in response to pressure on the piston 125. Specifically, application of positive pressure on the piston 125, for example, as directed by an operator at surface, may be utilized as the manner by which valve opening is achieved. That is to say, the valve assembly 101 is considered of a “normally closed” variety. Thus, where pressure is removed, whether intentionally or by an intervening condition such as loss of pressure control, the piston 125 will recede back to its seat 122 and the valve 190 will automatically close.

As detailed hereinbelow, the piston 125 is outfitted with an interfacing element 100 configured to durably achieve sealed closure as the piston 125 interfaces the seat 122. Thus, reliable sealed closure of the valve 190 therebelow may be achieved when positive pressure is removed from the line 120 above the piston 125. Once more, the interfacing of the piston 125 and seat 122 may be achieved without undue damage or resulting wear to the element 100. Therefore, repeated reliable closure of the valve 190 may be expected over a more extended period of use.

Referring now to FIG. 2, an enlarged view, taken from 2-2 of FIG. 1, reveals an embodiment of the interfacing element 100 in relation to its interfacing of the valve seat 122. In this view, the piston 125 is shown forcibly directed downward away from the seat 122 to a degree by the influx of fluid pressure 250 through the hydraulic line 120 from a location above the seat 122. As indicated above, this may be affirmatively directed by an operator at surface. In this manner, the controlled downward shift of the piston 125 may ultimately be translated into the opening of the valve 190 as described above with reference to FIG. 2.

Continuing with reference to FIG. 2, the interfacing element 100 is shown outfitted with a seal ring 200. The ring 200 is of a durable non-elastomer such as copper, brass, polytetrafluoroethylene (PTFE) or other suitably robust material. Thus, once the fluid pressure 250 is removed and the element 100 is allowed to contact the seat 122, a flush sealable interfacing may be achieved in a manner that does not unduly damage or impair the top of the element 100.

Referring now to FIG. 3, maintaining a sealed interfacing between the element 100 and the seat 122 may involve more than the durable flush interfacing provided by the ring 200. More specifically, FIG. 3 reveals an enlarged view of an embodiment of the element 100 taken from 3-3 of FIG. 2 wherein an underlying energizing component 300 is disposed. That is, the element 100 includes a ring 200 for durable sealing at the interface with the seat 122. However, an elastomeric, biasing form of the energizing component 300 is disposed below the ring 200 so as to ensure maintenance of the seal capacity of the piston 125 relative the seat 122. Of course, the energizing component 300 may take alternate forms such as a metallic spring or other mechanism of suitable energizing character.

Continuing with reference to both FIGS. 2 and 3, the removal of the fluid pressure 250, whether intentional or due to an emerging condition, allows the piston 125 and element 100 to shift upward and attain the described seal. This can be seen in reference to FIGS. 4A and 4B, where the spring 185 is allowed to expand from the position of FIG. 4A to that of FIG. 4B upon removal of the noted pressure 250 of FIG. 2. However, in order to avoid the effects of possible undulating or other slight vertical movements of the piston 125 following the initial sealable contact between the ring 200 and seat 122, the underlying energizing component 300 is provided as described below.

With particular reference to FIG. 3, an elastomeric energizing component 300 is shown sandwiched between the ring 200 and the main body of the piston 125. This component 300 may be of rubber, polyether ether ketone (PEEK) or other suitably deformable material of energized or re-formable capacity. Thus, as the above described seal between the ring 200 and the seat 122 is attained, slight vertical movements of the piston 125 may be responsively accounted for in a manner that maintains the seal. So, for example, as the piston 125 moves upward, the component 300 is squeezably deformed as depicted in FIG. 3 and the seal attained. However, a slight movement downward does not translate into breaking of the seal, compression of the spring 185 or ultimately cracking open the valve 190 further below (see FIG. 1). Rather, such natural undulating of the piston 125 is more likely to result in the repeated deformation and reformation of elastomeric component 300 morphology without sacrifice to the seal.

Once more, the intact seal between the ring 200 and seat 122 is achieved in a manner that avoids undue wear on the underlying component 300. That is to say, rather than utilize the component 300 to provide seal capacity in addition to the described biasing and energizing effect noted above, a durable intervening seal ring 200 is provided. As a result not only is the seal maintained but the element 100, and indeed the entire assembly 101, may be repeatedly used without requiring change-out and/or component 300 replacement every few times the valve 190 is closed (see FIG. 4B).

Referring now to FIGS. 4A and 4B, side sectional views of an embodiment of a valve assembly 101 are depicted. More specifically, FIG. 4A depicts the assembly 101 having a valve 190 and corresponding flapper 490 thereof in an open position. FIG. 4B on the other hand depicts the valve 190 and flapper 490 closed following removal of internal positive pressure.

With particular reference to FIG. 4A, positive pressure is maintained on the piston 125 via fluid 250 through the internal hydraulic line 120 of FIGS. 1 and 2. As such, the spring 185 is compressed in a manner that conventionally translates to opening of the flapper 490 of the valve 190. Ultimately, this allows production fluid 400 to proceed in an uphole direction through a channel 110 of the assembly 101. That is, the channel 110 runs through the interior of the assembly 101 including the spring 185, housing 150 and other interior features, with access thereto governed by the open or closed position of the valve 190.

Continuing with reference to FIG. 4B, however, the valve 190 and flapper are now depicted in the closed position. This is achieved through the removal of the pressure applied to the piston 125 as noted above. As a result, the spring 185 is allowed to return to its natural, more expanded, state, thereby also allowing for the flapper 490 of the valve 190 to close. Thus, fluid 400 from downhole of the assembly 101 is no longer able to traverse the channel 110.

With added reference to FIG. 5, the closure of the flapper 490 of the valve 190, ensures that hydrocarbon fluids 400 are prevented from reaching an oilfield surface 500. As a practical matter, this may be particularly beneficial where the reason for the closure is due to the sudden emergence of a hazardous condition at or near the well head 527, perhaps resulting in loss of well control. Once more, the valve 190 may reliably remain closed in spite of minor fluctuations of the spring 185 or other internal assembly components, even in the substantial absence of supportive downhole pressure.

With added reference to FIGS. 1-3, this benefit of the assembly 101, for example, in particularly low pressure wells 580, is due to embodiments of the inclusion of the interfacing element 100 as detailed hereinabove. Indeed, embodiments as detailed hereinabove may be effectively employed in wells 580 having a pressure differential as low as about 10 PSI or less in the vicinity of the assembly 101. Furthermore, in addition to maintaining seal at lower pressures, the element 100 is also of a durable configuration as described above. Thus, not only is it effective on repeated use, but also at a wide range of downhole temperatures. For example, embodiments as detailed hereinabove may be effectively used in well environments ranging anywhere between about 40° F. and about 350° F. without concern over undue wear and/or resultant failure.

Referring specifically now to FIG. 5, an overview of an oilfield 500 is depicted with a well 580 accommodating the above referenced assembly 101 therein. The well 580 traverses a formation 590 and is defined by casing 585 down to an open-hole area that includes a perforated production region 595. Nevertheless, the well 580 is relatively low pressure in nature, perhaps generally below about 50 PSI. Thus, an electrical submersible pump (ESP) 575 with electrical line 550 to surface is provided as a manner by which to encourage hydrocarbons into production tubing 581 (e.g. at a location below an isolating packer 560 thereof).

A host of oilfield equipment 520 is disposed at the oilfield surface 500. In the embodiment shown, this includes pressure regulating equipment 525, an operator control unit 522 and a well head 527 from which the noted production tubing 581 is deployed. A production line 529 is also shown emerging from the well head 527 for transport of produced fluids. Additionally, a rig 521 is depicted which may support a host of different types of interventional applications over the life of the well 580.

Continuing with reference to FIG. 5, a surface controlled subsurface safety valve assembly 101 is incorporated into the noted tubing 581 adjacently below the surface located well head 527. Thus, via the control unit 522, an operator may direct valve closure so as to halt production through the tubing 581 and assembly 101. This may take place for the sake of an interventional application, in response to a detected downhole condition, or for any number of reasons. Once more, should well control be suddenly compromised or lost at the regulating equipment 525, well head 527 or elsewhere, the assembly 101 may automatically close off production therethrough as detailed above. That is, the hydraulic pressure from surface which keeps the assembly 101 open may be automatically halted resulting in valve closure. Once more, due to the unique internal element 100 of the assembly 101, the low pressure condition of the well 580 does not result in measurable continued production migrating uphole beyond the assembly 101. Thus, follow-on intervention, work-over or remedial action may be pursued at surface without concern over any interfering unintentional production.

Referring now to FIG. 6, a flow-chart summarizing an embodiment of employing a surface controlled subsurface safety valve assembly is depicted. Namely, as indicated at 615, the assembly may be installed in a well. For example, the valve assembly may be incorporated into installed production tubing. Therefore, in order to allow for production through the tubing as noted at 645, the valve assembly may be affirmatively opened as directed from the oilfield surface (see 630).

Once production is to be halted, the valve assembly may be closed based on surface conditions. That is, whether through operator direction (660) or as a result of an emergent well control issue (675), the assembly may be closed so as to safely halt production. In fact, even in circumstances of low well pressure or widely varying downhole temperatures, maintaining of the closure may be reliably assured. As indicated at 690 this is due to the aid of a durably energized valve element of the assembly.

Embodiments described hereinabove include a subsurface safety valve configured to achieve effective sealable closure. This remains the case even in the face of particularly low pressure well environments which lack any significant valve closure aid in the form of downhole pressure. Once more, this may be achieved in a robust and repeatable manner without undue concern over premature valve failure due to degrading energizing valve components.

The preceding description has been presented with reference to presently preferred embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle, and scope of these embodiments. Regardless, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope. 

1. A surface controlled subsurface safety valve assembly comprising: a hydraulic line running from an oilfield surface; a valve housing coupled to said line at a valve seat thereof; and an interfacing element disposed in said housing for closing upon the seat and having an energizing component adjacent a non-elastomeric seal ring for meeting the seat upon the closing.
 2. The valve assembly of claim 1 wherein the seal ring is of a material selected from a group consisting of copper, brass and polytetrafluoroethylene.
 3. The valve assembly of claim 1 wherein the energizing component is selected from a group consisting of a spring and an elastomeric material.
 4. The valve assembly of claim 3 wherein the elastomeric material is selected from a group consisting of rubber and polyether ether ketone.
 5. The valve assembly of claim 1 further comprising: a central channel disposed in said housing for guiding fluid from a location below the assembly to a location above the assembly; and a valve disposed in said channel for regulating the guiding.
 6. The valve assembly of claim 5 wherein said valve is a flapper valve.
 7. The valve assembly of claim 5 wherein said interfacing element is disposed at an end of a hydraulic piston located in said line for coupling to said valve.
 8. The valve assembly of claim 7 wherein the coupling is provided by a responsive element disposed between said piston and said valve.
 9. The valve assembly of claim 8 wherein the responsive element is a spring for compressibly opening said valve in response to movement of said hydraulic piston in said line.
 10. A fluid control system for use at an oilfield, the system comprising: well control equipment disposed at a surface of the oilfield; a tubular disposed in a well at the oilfield and coupled to said equipment; and a safety valve disposed in said tubular and having an element with energizing and non-elastomeric components for substantially maintaining a sealed interface at a seat of said valve during closure thereof.
 11. The system of claim 10 wherein said valve is rated to substantially maintain the closure at well pressure below about 50 PSI.
 12. The system of claim 10 wherein said valve is rated to substantially maintain the closure at well temperatures of between about 40° F. and about 350° F.
 13. The valve of claim 10 wherein said tubular is a production tubular.
 14. The valve of claim 13 wherein said equipment is a well head, said safety valve disposed subsurface within said production tubular adjacent said surface disposed well head.
 15. A method of regulating subsurface fluid flow in a well from a surface location adjacent the well, the method comprising: closing a safety valve in the well to prevent fluid flow therethrough, said closing including allowing sealing of an internal piston of the valve at a valve seat of the valve; and substantially maintaining said closing by way of an interfacing element of the piston having an energizing component adjacent a non-elastomeric seal ring, the ring to meet the seat for the sealing.
 16. The method of claim 15 further comprising directing an opening of the valve from the surface location prior to said closing.
 17. The method of claim 16 wherein said directing comprises maintaining hydraulic pressure on the piston throughout a duration of the opening.
 18. The method of claim 15 wherein the sealing is powered by a spring coupled to the piston and configured to responsively expand during the allowing.
 19. The method of claim 15 further comprising directing said closing from a control unit positioned at the surface location.
 20. The method of claim 15 wherein said closing is automatic in response to an emergent condition of equipment positioned at the surface location and in fluid communication with the safety valve. 